GuessEncoding function

Declaration

function GuessEncoding(const s: string): string

Arguments

Function result

Encoding name detected, or a default value.

Description

GuessEncoding is a String function which tries to determine the encoding used for the value specified in S. The return value contains an encoding name, like 'utf8' or 'ISO-8859-1'. It may contain an empty string ('') when S is also an empty string.

GuessEncoding checks S for various Byte Order Marks at the start of the value, including: UTF8BOM, UTF16LEBOM, and UTF16BEBOM. When present, the BOM determines the encoding used for the value.

Finally, it checks for a valid UTF-8 encoding (which includes ASCII characters). All characters in S are examined until a character whose UTF-8 code point is not valid is encountered.

If encoding cannot be determined, the default encoding for the platform is used. When it is EncodingUTF8, it is changed to 'ISO-8859-1'. This is done because the system may use the UTF-8 encoding, but the value in S does not. ISO 8859-1 has a full mapping to Unicode, and this prevents data loss in encoding conversions.